It is quite unfortunate that Udemy prices their courses the way that airline industry prices airplane seats - depending on which direction the wind is blowing, on any particular day. If you are an existing customer, you will get emails with prices that are different then what they are offering to you on that other email account that you also signed up but never bought anything with.
The most annoying part is that when you find that crazy moment, when you want to learn something totally new and different, the price might be $200 but you know that if you wait a few days (week a max) they will be emailing you with whatever is in the link, that results in the same course being $10. You look at all of that and in disgust you end up scratching that itch with Netflix.com and/or Pluralsight.com.
Udemy is killing their own sales with such immature pricing tactics. Either that or too many of us are too immature and end up paying the grossly over-inflated prices.